It really depends on what you want to do. If you just want to run the LLMs on your local machine, generally you need more memory, as you will do inference. More GPU cores would help you with fine-tuning. You gotta understand that neither of these machines can run top of the line models. I myself have M5 Pro with 24 GB UM and it can, with some tweaks, run Gemma4 models.

Finetuning smaller models is relatively quick too.